The present invention relates to a technology for remote copying among storage subsystems.
Now that we live in an information society where the rapid spread of the Internet, the advent of broadband services and corporate mergers have all combined to complicate the operation and management of systems and where a huge volume of data is being handled, there is a growing demand for a system that can be restored quickly in the event of a disaster during a continuous operation 24 hours a day, 365 days a year. To meet this demand a technology is available which can make copied volumes (hereinafter referred to as sub-volumes) in storage subsystems located at remote places through communication lines. With this technology it is possible to recover data quickly from remote places and resume the system operation. Such a technology is disclosed in JP-A-11-85408 for example.
A currently available remote copying technique involves a computer sending update data to a local site and also to a remote site. This is done only for guaranteeing the data update for each input/output operation.
Thus, when an application program on the computer updates data files stored in a plurality of volumes and if the copy processing is interrupted by a communication line failure during the process of updating logically significant data, the data in the sub-volumes at a copy destination may become incomplete when seen from the application program even if the data update is guaranteed for each input/output operation.
In resuming service using the sub-volumes at the remote site having such invalid data, the data in the sub-volumes needs to be recovered using a journal on the application program side before the service can be resumed.
This invention therefore provides an information processing system that, in the remote copying process, can assure an updated data consistency for each process or task.